Sunday, 28 June 2009

Bowdrill experiments

Whoa, ho, ho, ho - sinister Peter Cushing-type laugh. Time for a little experiment. Enough of this nonsense.

I had some bits and pieces of wood lying around drying out that were just begging to be abused. So I dug out a pine hearth, a hazel drill, a holly drill and my trusty teak bearing block (salvaged from an old table leg). I decided to go against the grain and have a little experiment with drill shape. I fly in the face of convention, ha!

In one of Ray Mears' books he says that the rounded end of the drill should go in the hearth because of greater friction and the pointy end should go in the block because of less friction. Seems logical but I was bit bored and decided to have a go with my rather eclectic mix of kit. My thinking was this, if the pointy end was in the hearth then due to its smaller circumference you would achieve faster rotations relative to the amount of effort put in. You would also be able to apply proportionately greater pressure for the same amount of force due to its smaller surface area. Elementary physics something to do with woman in high heels, elephants and who you would prefer to be stood on by! I believe that there are specialist websites for that sort of thing. I'm not sure what happens if the elephant is wearing heels though?

By contrast having the rounded end in the block means that it generates less heat due to slower rotation speeds even though it is presenting a larger surface area. Of course my physics could be completely cr*p!

Either way I went for it. I managed smoke very easily and after a couple of passable attempts at recreating the bouncing bomb effect with flying drills I got a really good ember. This worked for both the hazel and holly drills and didn't take much effort. The reverse configuration seemed to work well though the penalty was greater wear on the pointy end.

An interesting way to spend an hour on a sunny Saturday afternoon. The question is - has anyone else flown in the face of wisdom and tried doing it differently (the bowdrill that is)?

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2 comments:

Pathfinder said...

Hi Jon

This method is used at the Tracker School with Tom Brown and is one I have used myself, it is good for burning down quicly. Nice one buddy good to see someone pushing the limits of thier thinking and not just conforming.

Aye

Geoffrey

Jon said...

Thanks mate - deep down I've always been a bit of a rebel on the QT!